1. Field of the Invention
The present invention relates generally to the field of fluid pumping mechanisms. More specifically, the present invention is useful in an embodiment as a fuel pump wherein an impeller rotates in a housing for pumping fluid.
2. Description of the Related Art
Such feed pumps are known as peripheral or side-passage pumps and are used, for example, in modern motor vehicles for feeding fuel or washing liquid. During rotation of the impeller, the guide blades in the feed chamber produce a circulation flow running transversely to the direction of movement of the guide blades. The circulation flow enters the blade chambers in the radially inner region of the impeller and discharges from the blade chambers in the radially outer region. To adapt the feed pump to an intended characteristic and to the viscosity of the liquid to be fed, the angle of inclination of the guide blades and the chamber volumes can be calculated and adapted. This adaptation is decisive for the efficiency of the feed pump in the intended application.
A disadvantage with the known feed pump is that vorticity is induced in the circulation flow upon entry to the blade chambers. These vortices lead to a disturbance in the circulation flow and thus to a low efficiency of the feed pump. Furthermore, the circulation flow has an especially low pressure in the entry region of the blade chambers, so that, for example, liquids which are close to their boiling point may vaporize due to the vortices and may thus reduce the efficiency of the feed pump to an especially pronounced degree. In particular, the feed pump used as a fuel pump in a motor vehicle therefore often has a very low efficiency.
The problem underlying the invention is to design a feed pump of the type mentioned at the beginning in such a way that vortices are kept especially small and that the feed pump has as high an efficiency as possible.
This problem is solved according to the invention in that the feed chamber is designed for directing the liquid from a radially inner region of the impeller into the blade chambers.
Due to this design, deflection of the circulation flow upon entry to the blade chambers is avoided. Since the flow is accelerated to an especially high degree in the radial direction inside the blade chambers in accordance with the design of the guide blades, vortices are markedly reduced by the radial entry of the circulation flow into the blade chamber. As a result, the liquid to be fed does not tend to vaporize. For this reason, the feed pump according to the invention has an undisturbed circulation flow and thus an especially high efficiency.
The feed pump according to the invention turns out to be of especially simple design if the guide blades project into the graduated-ring-shaped passage. In the feed pump designed as a peripheral pump, the circulation flow can hereby be directed precisely from inside to outside through the blade chamber.
In another advantageous development of the invention, the impeller is designed as a flat component which can be produced in an especially cost-effective manner if the impeller has a groove in its region adjoining the guide blades radially on the inside. As a result, the incident flow to the guide blades takes place at least partly via the groove.
In order to avoid overflow of liquid to the inlet passage, the circulation flow must be interrupted downstream of the outlet passage as viewed in the direction of rotation of the impeller. Overflow of liquid from the outlet passage to the inlet passage via the groove in the impeller can be avoided in a simple manner if the housing has a projecting web penetrating into the groove of the impeller.
The web could be arranged, for example, solely between the outlet passage and the inlet passage and designed to fill the groove. However, in another advantageous development of the invention, the web has high stability if the web is of ring-shaped design and has a widened portion outside the region of the graduated-ring-shaped passage, the widened portion filling the groove. Furthermore, the groove may thereby have an appropriate width for cost-effective production of the impeller. In addition, the impeller has an especially low weight and thus a low inertia due to this design.
In another advantageous development of the invention, vortices inside the feed chamber can be reduced further if a guide element for directing the flow in the feed chamber is arranged in the groove and/or on the web.
In another advantageous development of the invention, uniform acceleration of the circulation flow in the blade chambers can be achieved in a simple manner if the guide blades, in their radially inner region, have an entry bevel pointing in the direction of rotation of the impeller. This helps to keep vortices of the circulation flow especially small.
The feed pump according to the invention, which feed pump is intended as a fuel pump, has an especially high efficiency if an angle of inclination of the entry bevel is approximately 55xc2x0 to 70xc2x0, preferably 60xc2x0, relative to the remaining region of the guide blade.
The circulation flow enters the blade chambers with an especially low velocity if the guide blades have a smaller wall thickness in their radially inner region than in their radially outer region. Furthermore, this helps to further reduce the vortices when the circulation flow strikes the guide blades.
In another advantageous development of the invention, guidance of the circulation flow in the intended manner can be reliably ensured if a housing part carrying the web and a housing part mounting the impeller have centering grooves and centering webs engaging one inside the other.